A nonreturn valve of this type is used to realize the difference between the compression and rebound movement of a shock absorber. This is because during the compression movement the shock absorber must impart less flow resistance to the fluid that is to be displaced from one side of the piston to the other side of the piston, i.e. from the second chamber to the first chamber. During the rebound movement, there should be a greater resistance, which constitutes a significant part of the shock-absorbing action of the shock absorber. Various types of shock absorbers have been proposed for this purpose in the prior art.
In JP 58211038 a damper is disclosed. Above (i.e. the direction of moving the piston from the cylinder) the valve seat and the plates acting thereon, a spring-loaded auxiliary structure is provided. This auxiliary structure comprises a ring having a smaller external diameter than the surrounding housing, so that there is always a fluid connection along said spring-loaded structure. A valve plate can be moved there against, being provided at the inner circumference thereof with radially extending projections. The recesses realised in this way do not cooperate with the seat as described above, but cooperate with a further plate assembly being positioned under the flexible plate.
In US 2005/0211087 prior art is discussed, comprising a shock absorber wherein during outward movement of the securing means at the extremities of the shock absorber, a normally open flow passage is closed by a flexible valve plate being displaced against a seat. This closing movement is effected in a single step, i.e. all along the circumference of the displaceable valve plate at a single moment sealing on the valve seat is effected.
The subject invention aims to provide a shock absorber wherein the closing movement described above at moving from each other of the securing means is effected more gradually in order to provide a higher comfort.